Electrical cable and method for manufacturing the same



June 28, 1932. v, WODTKE 1,865,415

ELECTRICAL CABLE AND lEfi'HOD FOR MANUFACTURING THE SAME Filed April 7, 1923 4 Sheets-Sheet 1 in; v If bgt) 6 K i w o M 83 o o an :ill 1 o A.

n INVENTOR hwfllm ,%4 ATTORNEYJ H. V. WODTKE June 28, 1932.

ELECTRICAL CABLE AND METHOD FOR MANUFACTURING THE SAIE Filed April 7. 1923 4 Sheets-Sheet '2 IN V EN TOR BY ATTORNEYS H. V. WODT KE June 28, 1932.

ELECTRICAL CABLE AND METHOD FOR IANUFACTURING THE SAIE Filed April 7, 1923 4 Sheets-Sheet 3 I N VEN TOR June 28, 1932. v WQDTKE 1,865,415

ELECTRICAL CABLE AND METHOD FOR MANUFACTURING THB1SAIE Filed April 7, 1933 4 Sheets-Sheet 4 v v IN VENTOR 'gb V QM,

ATTORNE Y5 Patented June as, 1932 mm s 'rA 'rss PATENT orrlcs.

7 ms v. worm or-nmuo. mrw You assrsnon. arms 'mmmum ;-ro emtmur. cum oonromrron. or new rear, x. r. a ooaromrron or raw ans]! mnprnrnon iron. murac'rumo m am Application 11.; April 1, 1m. Serial Io. no.4.

The present invention relates to improvements in the art of manufacturing electrical cables having a' com oundor the T e invention is illustrated in connection with an electrical'cablewhich consists of a core, com risinga plurality of twisted insulated con uctors with fillers arran ed therebetween to round out the core, an a covering made up of a plurality of layers of rubber compound vulcanized together and onto the core with a reinforcing li ature arranged between the adjacent la ers the rubber. It should be understood, owever, that the invention is not limited to the roduction of this particular cable, as the met od may be used so with parts broken away to more clearly disto produce cables of various other constructions, as will appear later in the description.

This application is related to my copending application Serial Number 629 406, filed April 2, 1923, the present application being directed more articularly to the cable making art while t e other ap lication is directed more particularly to t e molding art in general. I

In the drawings:

1 is a plan view of the mechanism for covering the core Fig. 2 is a side elevation of this mechanism close the construction;

Fig. 3 is a vertical sectional view on the line 33 of Fig. 1 but on a larger scale than Figures 1 and 2; i

Fig. 4 is .a similar view onthe irregular line4-4ofFi .2;

Fig. 5 is a side elevation of the vulcanizing mechanism;

Fig. 6 is an end view thereof;

Fig. 7 is a horizontal section through one of the heating elements for the mold plates;

Fig. 8 is an enlarged perspective view of the rolls for forming the rubber on the core and removing the surplus.

Fig. 9 is a detail erspective view of the particular form of ca 1e which is selected for the illustration of this invention with successive layers progressively removed to show the interior construction; and

Fig. 10 is a detail showing the manner in plastic covering of rubber ike and to the article itself.

which the covering ofrubber compound is apphed to the core.

The cable illustrated inthe drawings (Figs. 9 and 10) in progressively broken away sections includes a core comprisin insulated twlsted conductors 1 between WlllCh fillers 2 are arranged to round out the'core. The covermg for this core includes a plurality of layers of rubber indicated in the drawin by the characters 3, 4 and 5. Ligatures 6 w ich are for the purpose of increasing the tensile strength of the cable are arranged between two of the layers of r ibber.

The illustrated form of the mechanism for applylng the covering to the core which is shown 1n Figs. 1 and 2includes a bed 10,'at the left or incoming end of which is located a reel 11 adapted to support a rolled strip 12 of uncured rubber compound which subsequently forms the preliminary covering for the core. Mechanism for applyin this prel minary covering to the core, and or removing the surplus compound therefrom is supported on the bed 10 adjacent to the reel.

11. This mechanism includes a pair of cooperating removable rolls 13 and 14, su

pprted on shafts 15 and 16, which have them arings in standards 17 and 18. Bearings 19 and 20 are vertically movable within the standards 17 and 18 and are removable therefrom to permit the substitution of other rolls when it is desired to operate on a different size or character of cable. The adjustment of these rolls and the securement of the same in their adjusted positions is attained by means of wedge blocks 21, and set screws 22 and 23.

The shafts 15 and 16, and consequently the rolls 13 and 14 mountedthereon, are driven in opposite directions, the roll 14 being driven by a gear 24 which receives its motion from a cooperating gear 25 mounted on a shaft 26, as shown in dotted lines in Fig. 2, extending transversely of and mounted in bearings on the bed, which shaft is actuated by bevel gear 27. This latter gear receives its motion through a inion connection 28 with a driven shaft 29, w ich shaft is actuated in a manner later to be described. The upper roll 13 is rotated by a train of gears 30 between the shafts 15 and 1e.

The core of the cable (see F1 9) is fed to this mechanism and the uncured rubber com- 8 pound from the reel 11 is folded around the core before it reaches the mechanism. Th s coverin 3 tShsee Fig. is 1 applied longitudinalfy to e core so that the meetintggdges 32 extend along one side thereof. In case 10 of larger cables two strips of covering compound may be used to form each sheath. The rolls 13 and 14 are each (provided with an intermediate groove 33 an with side grooves 34 and 35, the grooves being separated by rid s 36 and 37. v

e core to which the preliminary covering 3 has been applied is fed to the rolls 13 an 14, the core itself passin between the cooperatin ves 33 of t e two rolls. The excess ru r which is present at the meetin edges 32 on one side of the core is pinched ofi by the cooperating ridges 37, the excess passing between the rolls through the cooperating grooves 35. The opposite side of t e covering is pinched between the cooperating ridges 36, so that the covering is drawn tightly about the core, the excess rubber which is pinched ofi of this. side of the covering passing between the rolls in the grooves 34. These excess strips of the rubber covering which are represented at 38 in Fig. 8 of the drawings pass downwardly after leaving the rolls 13 and 14, are stripped from the cable, and are fed away by a pair of cooperating rollers 39 and 40, the roller 39 being positively driven and the roller 40 being spring pressed against the former. This roller 39 is driven by a belt 41, which receives its motion from a ulley 42 mounted inside the end of the bearmg 43 shown on the left hand of Fig. 1, and ri 'dly secured to shaft 15 adjacent the roll 13. cans, which is su ported on the bed 10 and located in spaced re ation to the mechanism just described, is provided for applying ligatures 6 over the preliminary rubber covering of the core after the latter is fed through the first rolls 13 and 14. This means includes a revoluble plate 45 which is mounted on a hollow shaft 46, the latter being driven by a belt and pulley connection 47 with the driven shaft 29. The plate 45 is provided with an opening which is aligned with the opening of the hollow shaft 46. The covered core is fed from the rolls 13 and 14 through the hollow shaft and through the openlng in the plate.

Arranged concentricall on the plate 45 is a series of spools 49 whic bear the ligatures and which upon the revolution of the plate and the longltudinal movement of the cable along the mechanism apply the li tures to the outside of the preliminary rub r coverin and under tension, preferably in a convo ute form.

Located between these ligature bearing spools and a second mechanism 48 for appl ing a second layer of rubber and removing e surplus is a second reel 50 which supports a second roll of uncured rubber ta 51-. This tape is applied to the moving ca e over the ligatures which have been applied to the preliminary mvered core. This mechanism 48 is actuated by a gear connection 48 with the shaft 29.

shaft 29 is actuated from the lower roll shaft ofthis rubber removing mechanism by a bevel gear 59 which intermeshes with a pinion 60.

The arrangement of mechanisms illustrated is for the purpose of forming the particular cable illustrated but it is to be understood that if it is desired to increase the thickness of the rubber covering or the number of ligatures the mechanisms for appl 'ng the same may be rearranged accordin y.

The cable passes around a drivin s eave 60', which is positively driven by t e shaft 29 through a gear connection 61. From the driving sheave 60, the cable passes to a reel, not shown, on which it is Wound. The driving sheave 60 thus cooperates with the covering rolls to draw the cable through the various rubber and ligature applying mechamsms.

The rubber covered and ligature bound core, after being wound on the reel, not shown, is subjected to the action of a vulcanizing mechanism such as shown in Figs. 5, 6 and 7, where the rubber is cured so that the ligature and all of the several covering elements become an integral cover and so that the cover and core are unified.

This mechanism includes relativel movable platens 61 and 62 carrying mold plates 63 and 64, the platens being forced together by suitable mechanism which is illustrated in the drawin s as hydraulic rams 65.

The mol plates are each provided with at least one groove 66, the corresponding grooves in the plates cooperating to form a com lete mold for the cable.

T e platens are provided with intermediate heating chambers 67 and end chambers 68 and 69. A circulation of a heat exchange medium such as steam is maintained through the intermediate chambers by conduits 70 and 71. The end chambers 68 and 69 are each provided with an inlet conduit 72 and an msm.

Satisfactory vulcanization of the rubber compound has, however, been obtained when steam is circulated through the chambers '67, water circulated through'the chambers 68 and the chambers 69 supplied with air.

The result ofthe heating of the chambers 67, 68 and 69 is the raisin of. the temperature'of the mold plates an the gradual reduction or to. ring 03 of the temperature toward the 'en s of the lates. The temperature ofthe mold plates between the chambers 68, 68 rises aduall from the extreme outer ends of the plates roughout the length of the chambers 68 to a lme over the steam chambers 67 which may be approximately in-\ dicated by the line AA. At, the other end the temperature is gradually reduced from a Y endof the mold plates.

diately closed by the constantly acting hy- In carrying out the vulcanizing ghase of this method an integral section o t e cable, 611181 in length to that of the mold plates, is p aced between the plates in one of the .grooves. The plates',.being heated, are forced toward each other until they compress the rubber covering andare thus maintained un til the vulcanization is completed, thepressure being continuously exerted. The succeeding sections are then drawn between the plates and vulcanized. A plurality of cables are thus treated simultaneously.

The cable which is placed between the mold plates is larger than the molds in which it is vulcanized, so that during the vulcanizaelectrical cables manufactured 1n accordance tion and the exertion of the pressure by the mold plates some of the rubber exudes between the ridges of the plates in thin sheets which extend longitudinally along the sides of the cable after the vulcanization has been completed. As the rubber softens the thinridges are forced closer together making it increasingly difficult for the rubber to escape. Thus the tendency of the rubber to expand internally by the formation of numerous air kets is counteracted because as soon as e airpockets begin to form they are immedraulic pressure. With a bolted-up mold the air pockets are free to expand by merely forcing softened rubber'out through the same sized egress space as existed when the rubher was colder and harder.

The bulk of these sheets of excess rubber is stripped from the cable after its vulcanization has been completed but there inevitably remains on the sides of the cable thin ridges or fins which are among the distinguishing outer end of the chamber 68 1 to reduce. Thus the features of the cable made I the resent-invention. v

en after the cu of a'sectio'n of the covering the next adjoining section'is moved into position between the mold plates, the int on the cable which is located at the at the incoming end of the machine where the tem rature is the lowest which int is marked (Fig. 7), is drawn through tween the mold lates to the line BB at the outgoing end 0 the machine, where the tem rature of the mold plates over the steam c amber 67 just be ins ortion-of the 1111 her which is subjected tot e eatest heat adjacent the incoming end of t e machine is subjected to' the least heatat the outgoing end, and that which is subjected to the leastheat at theincoming end of the'machine is subjected to the greatest heat at the outgoing end. This step-by-step vulcanizing act1on is repeated until the covering of the entire cable has been vulcanized.

This graduation or tapering off of the temperature of the mold plates results in the production of a vulcanized covering which is substantially uniform in character, there being no definite lines of demarcation betweenthe successively vulcanized sections, but the character of the rubber betweensthe vulcanized sections being substantially the same as that of the sections.

Furthermore, the vulcanization of the cov-, ering under pressure forms the several layers of rubber covering into a homogeneous mass, in which is imbedded the ligatures 7. It. also causes the unification of the cable, that is to say, causes the adhesion of the covering to the 7 core and the permanent positioning of the core within the covering. Careful examination and test of insulated mass, which is to be distinguished from a product made up of the same elements but finished in bolted-up molds or by the socalled open steam cure. In the latter case the covering of rubber compound is not of uniform dimension and shows the effects of gassing during vulcanization; the surface eing pitted and the compound containing internal pockets of gas. By the method of vulcanization disclosed herein the tensile strength of the compound is very materially increased, this increase running as high as thirty-five rcent. Furthermore, the several layers of ompound cannot be separated or the compound separated from the core except by extreme manual force, whereas a simicure will readily peel away from the core and the several layers will readily as arate. As further indicating the superior aracter of the roduct of the present invention over the a pro not of the open steam cure, it is noted tent that the specific gravity of the entire cable is increased from oneto one and one-half percent and the specific dgravity of the rubber com ound is increase b as much as threeof one percent. he durability of the outer coverin is also improved, as is indicated by the act that the puncture resisting qualities are increased by as much assixteen percent.

While particular embodiments of the invention have been described, it is to be understood that the various chan in details may be made in the machine an in the method and also in the construction of the cable go itself within the scope of the subj oined claims.

Claims:

1. The method of forming an electrical cable includin a core and a covering therefor, which inc udes applying a rubber coverinfi to the core, drawing the cover tightly on t e core and removing the excess rubber therefrom, applyin a ligature to said covering, applying a rub er coverin over said ligature, drawing the coverti ht y and removing the excess rubber there rom, and subsequently curing the rubber coverin under pressure between heated platens-sub]ect to a continuously applied external force active throughout the period of vulcanization to reduce the size of .the covering.

2. An electrical cable comprising a core and a covering therefor consisting of a plu-' rality of layers of rubber compacted and vulcanized together between platens under live controllable resilient ressure.

3. An electrical ca 1e comprising a core and a covering of rubber compressed and vulcanized in a mold under live resilient controllable pressure with the reatest cross sectional dimension of the ca 1e at the juncture of the molds.

4. An electrical cable including a core and a rubber coverin molded thereon under active pressure su cient to remove gaseous voids whenever formed and particularly during that part of the vulcanizing period when the covering is decreasing in volume, the finished covering being very dense and substantially without as pockets or voids.

5. An electrical cable comprising a core and a covering therefor consisting of a plurality of layers of rubber and spaced ligatures embedded between the layers compacted and vulcanized together between platens under live controllable resilient pressure.

6. An electrical cable of indefinite length including a core and a rubber covering molded thereon in a mold of definite length under active ressure suflicient to remove aseous voids w enever formed and particu ar- April, 1928.

r HANS V. WODTKE. 

